The U.S. Navy has for decades deployed bottlenose dolphins to search for underwater mines and detect enemy divers. Now the versatile sea mammals and their San Diego-based trainers are preparing for an unprecedented challenge: locating some of the few surviving vaquita porpoises in Mexico’s Upper Gulf of California.

Members of the U.S. Navy Marine Mammal Program, the dolphins are part of a team being assembled on both sides of the border aimed at capturing live vaquitas — something that has never before been accomplished and with the final outcome far from certain. But for an international group of scientists determined to save the species from near-certain extinction, it represents a final hope.

Don Bartletti / Los Angeles Times

A highly trained bottlenose dolphin slides onto a beaching tray in preparation for transport to the open sea in San Diego, CA at the Space and Naval Warfare System Pacific.

A highly trained bottlenose dolphin slides onto a beaching tray in preparation for transport to the open sea in San Diego, CA at the Space and Naval Warfare System Pacific. (Don Bartletti / Los Angeles Times)

Spearheaded by Mexico’s Secretariat of Environment and Natural Resources, the plan involves removing vaquita from the open water in their habitat in the Upper Gulf of California, and keeping them safe from the illegal gillnets where they have often ended up as by-catch and drowned.

To carry out the capture, an international group of experts is expected to gather in San Felipe later this year, including porpoise and veterinary care specialists capable of monitoring the conditions of any vaquitas that would be caught. There are many uncertainties, such as whether the small sea mammal would even survive captivity.

The operation “has to be done in a very careful, staged manner, and if any one of those fails, it’s over,” said Barbara Taylor, a conservation biologist at the National Oceanic and Atmospheric Administration’s Southwest Fisheries Science Center in La Jolla.

Scientists say the vaquita population has dwindled over the past two decades — from 567 in an initial survey in 1997 to fewer than 60 today. Despite a massive conservation program launched two years ago by the Mexican government, the vaquita population has continued to fall at an alarming rate largely because of entanglement in the gillnets used for a rampant illegal fishery for totoaba, a large fish whose swim bladders fetch exorbitant prices in China.

The new approach is known as ex-situ conservation, and would involve placing vaquitas inside a protective pen off the coast of San Felipe, with the hope that they might have a better chance for survival. If all goes well, they might also breed and reproduce.

“You are really getting down to the last few vaquitas,” said Taylor, a member of the International Committee for the Recovery of the Vaquita, an international advisory group to the Mexican government. “We can’t afford to be slow about this. We have to give this our mightiest effort as quickly as possible.”

The vaquita can grow to four or five feet long and weigh up to 120 pounds. Paula Olson  NOAA

The vaquita can grow to four or five feet long and weigh up to 120 pounds. Paula Olson  NOAA

Rafael Pacchiano, Mexico’s environment secretary, announced the collaboration with the U.S. Navy earlier this month in an interview with the Mexican newspaper, Excelsior. “Without a doubt this will be the last call for the vaquita, and as President Peña instructed us, we are doing all we can to avoid its extinction,” the secretary said.

The U.S. Navy’s involvement followed a request earlier this year from Mexico’s navy secretary, Adm. Vidal Francisco Soberón Sanz to U.S. Navy Secretary Ray Mabus.

“Admiral Soberón sent a letter requesting some help to locate the vaquita,” said Mabus’ spokesman Patrick McNally. “So Secretary Mabus talked with our folks in the Marine Mammal Program. It seemed like it would be a good fit.” The cost is about $140,000 and comes out of the Navy’s “partnership fund” budget. “We have a lot of great partnership activities with Mexico, and this is an example,” McNally said.

Based in San Diego, the Navy Marine Mammal Program uses both dolphins and sea lions for a range of tasks, from finding and neutralizing underwater mines to detecting clandestine swimmers and divers in restricted areas.

Dolphins are skilled at locating things beneath the surface through echolocation, or sonar, which allows them to interpret the echoes of sound waves, as well as through their capacity for directional hearing underwater.

To test the plan’s feasibility, some of the program’s dolphin were flown earlier this year to San Francisco Bay off of Sausalito, “where there is a very predictable group of porpoises, it’s very well known when and where they will appear,” said Mike Rothe, head of the Marine Mammal Program. “We had success. Our dolphins were able to detect and report the presence of the porpoises.”

Rothe said that four Navy dolphins will be now “part of a large effort this spring that’s going to involve an international group that’s going to have a lot of different boats, a lot of different ways” to look for vaquita in the Upper Gulf. “There will probably be some aircraft, and there will definitely be some watercraft. We would be another capability searching for the vaquita.”

The dolphins will be flown to San Felipe, and remain in temporary floating enclosures, until directed to conduct a search of a certain area. If the search is at some distance from the enclosures, the dolphins would be initially transported by boat to the general vicinity.

“Our objective would be to have the dolphins swim part way to where the vaquita is, and then leap out of the water, and then swim back,” Rothe said. The dolphins would be able to detect the vaquitas by detecting the biosonar echos in the vaquitas’ air-filled lungs.

The operation, being planned for May, is the latest in a series of efforts aimed at protecting vaquita, a small porpoise that lives only in the rich and turbid waters of the Upper Gulf of California. The animals, which must surface to breathe, are not only rare but extremely shy and difficult to spot, as they splash little, travel in small groups, and avoid boats.

The search would take place two years after President Enrique Peña Nieto traveled to San Felipe in April 2015 to launch an expanded two-year gill net fishing ban in the vaquita habitat and start a compensation program for fishermen who have made their living in the region. The government also committed to stepped-up enforcement in this area, with Mexico’s navy joining the effort to crack down on illegal fishing.

But the challenge to discourage poaching has only grown with the rising demand in China for the giant totoaba fish, and the vaquita have continued to die as by-catch in the illegal totoaba nets. A letter from non-profit groups earlier this year said monitoring had been insufficient, and alternative “vaquita-safe” fishing gear was not being implemented.

The illegal activity has continued — as have efforts to curb it. Earlier this month, Mexico’s environment ministry and the World Wildlife Fund Mexico announced the removal of 103 abandoned fishing nets in Upper Gulf in an operation that involved collaboration with environmental groups such as the World Wildlife and the Sea Shepherd Conservation Society.

The society announced that that on a single day earlier this month its vessels worked with the Mexican navy to catch six fishing boats using prohibited nets in the vaquita habitat area to catch totoaba.

In recent days, leaders of World Wildlife Fund and the Sea Shepherd Conservation Society have spoken out against the plan to capture vaquita. “Removing the vaquita will allow the fishermen to intensify their exploitation of the endangered totoaba fish,” Capt. Paul Watson, Sea Shepherd’s Founder, wrote on his Facebook page.

But defenders of the plan say it is worth the effort — and the risk. NOAA’s Taylor said even as the vaquita capture plan moves forward, enforcement efforts and other programs also must continue. “It’s not a situation where you can give up on enforcement, and give up on getting nets out of the water.”